The daily amount of SARS-CoV-2 viral RNA flowing into the Metro Plant correlates closely with the number of new daily cases reported by the Minnesota Department of Health. The plant serves nearly 2 million people in Minneapolis, Saint Paul, and 64 other metro area communities.
The blue line and points show the total amount of SARS-CoV-2 viral RNA in wastewater flowing into the Metro Plant, in millions copies of the SARS-CoV-2 genome per person served by the wastewater plant, per day. Blue points are daily values; the blue line is a running average of the previous 7 days. The gray line shows the average of the previous 7 days of new reported COVID-19 infections in the seven-county Metro area per 100,000 residents. Case data are provided by the Minnesota Department of Health and downloaded from [USA Facts] (www.usafacts.org).
In December 2021, Omicron rapidly replaced Delta as the dominant SARS-CoV-2 variant of concern in influent wastewater at the Metro treatment plant in Saint Paul. Since early February, we have observed the appearance and increase of the Omicron sub-lineage BA.2.
This graph shows the frequency of SARS-CoV-2 variants in Metro Plant wastewater. This frequency is the percentage of the total viral RNA that was identified as being from each particular variant. Points are daily data; lines and shaded areas are averages of the previous 7 days.
The dominance of various SARS-CoV-2 variants has ebbed and flowed over time. The current dominant variant, Omicron, became dominant in late December. The total amount of SARS-CoV-2 virus in wastewater has also been higher during the Omicron wave relative to earlier periods of the COVID-19 Pandemic, consistent with higher case counts in the region.
This graph shows the measured number of copies per person per day of each variant in wastewater. Points are daily data; lines and shaded areas are averages of the previous 7 days. The gray area in the background is the 7-day average total viral load. Variant proportions do not always add to 100%, so slight discrepancies between the total viral load and that of the individual variants are expected.
Variant frequencies are inferred from the presence of key mutations in the SARS-CoV-2 genome. Alpha, Beta and Gamma frequencies are inferred from the presence of the N501Y mutation; Delta from the L452R mutation; and Omicron from the K417N mutation. Some variants share mutations: presence of K417N mutation before November 18 were inferred to be the Beta variant. The two sub-lineages of Omicron (BA.1 and BA.2) are distinguished by the HV 69/70 deletion: Omicron BA.1 contains both the K417N mutation and the HV 69/70 deletion. Omicron BA.2 has the K417N mutation but not the HV 69/70 deletion.